Welding of metals products such as stainless steel products may result in heat tint discoloration in the heat-affected zone of the stainless steel weld. The heat tinting is generally a thickening of the naturally occurring oxide layer on the surface of stainless steel. As heat tint colors are formed on stainless steel, chromium is drawn from below the surface of the metal to form a chromium rich oxide surface layer. This leaves the metal just below the surface with a lower chromium level. The reduction in the sub-surface chromium typically reduces the corrosion resistance of the steel. In order to restore the corrosion resistance of the finished stainless steel product, the weld heat tint needs to be removed.
It is common procedure to clean the weld to remove the weld heat tint, which typically results in rebuilding of the passive layer around the weld and the restoration of the corrosion resistance of the weld. The removal of heat tint from welds of stainless steel may be done by techniques such as using pickling pastes, wire brushing, grinding or electrolytic methods. The use of pickling pastes can be hazardous while brushing and grinding is a labor-intensive process, leaving electrolytic methods as usually a safer, faster and more cost effective way for cleaning welds.
Existing welding cleaning systems that make use of electrolyte methods typically use a brush with electrically conductive bristles, such as bristles made of carbon fiber strands, which is supplied with an electric current and an electrolyte solution. When the carbon fiber tipped brush with the electric current and electrolyte solution is applied to the welded area affected by heat tint, an electrochemical cleaning of welded area occurs. Weld cleaning systems of this type are used to clean welds which were formed using gas tungsten arc welding, also known as tungsten inert gas (TIG) welding.
A popular type of welding is gas metal arc welding, also known as metal inert gas (MIG) welding. However, a problem with existing weld cleaning systems is that for the cleaning systems to clean a MIG weld a higher current is usually required, when compared with the current level required to clean a TIG weld. When a higher current is required, the carbon fiber brush wears down faster requiring the brush to be replaced more frequently. The frequent replacement of the carbon fiber brush can be problematic, as carbon fiber brushes are relatively expensive.
Therefore, given the relatively high cost of replacing a brush in a weld cleaning system, there is a need in the industry to provide an apparatus and process that alleviates, at least in part, the deficiencies with existing apparatuses and processes for cleaning welds.